A three-dimensionally oriented π-conjugated system;: synthesis and characterization of porphyrins bearing π-conjugated pendant strands

Three-dimensionally oriented rr-conjugated systems were constructed by the introduction of four aniline trimer pendant strands at the meso-position of the porphyrin scaffold. The atropisomers (alpha alpha alpha alpha and alpha beta alpha beta) were isolated and spectroscopically characterized. The H-1 NMR and UV-vis spectra revealed that the strands of the alpha beta alpha beta-isomer might be in equilibrium with the conformers, in which one or more strands lean toward the porphyrin ring. In the fluorescence emission spectra, the emission from the porphyrin moiety was almost completely quenched in the alpha alpha alpha alpha- and alpha beta alpha beta-atropisomers. (C) 2000 Elsevier Science Ltd. All rights reserved.